Power vehicles for carrying out diverse tasks are known. For instance, power lawn mowers are well known for use in turf and lawn maintenance. Such mowers may range from small, walk-behind mowers such as those used by homeowners, to professional grade riding mowers adept at mowing correspondingly larger areas. Between these two categories lies what are commonly referred to as “mid-size” mowers.
Generally speaking, mid-size mowers are self-propelled units having a cutting width of approximately 36-60 inches and are typically configured as either riding (e.g., ride-on or stand-on) or walk-behind units. While the present invention is directed to a velocity control system for use with a wide variety of riding or walk-behind vehicles, it will, for the sake of brevity, be described with respect to mid-size mowers.
Modern mid-size mowers incorporate a prime mover (e.g., internal combustion engine) and a hydraulic drive system. The drive system may include left and right hydraulic motors coupled to left and right drive wheels, respectively. Power may be transmitted from the prime mover to the left and right hydraulic motors, e.g., via one or more pumps, to drive the left and right drive wheels independently. The rotational speed and direction of each drive wheel may then be controlled by associated drive control levers under the control of an operator. By manipulating the control levers independently, each drive wheel can be separately driven forward or backwards at varying speeds. Thus, the mower may be propelled forwardly or in reverse. By powering one wheel in the forward direction and slowing, stopping, or powering the opposite wheel in the reverse direction, the mower can execute a turn.
Each drive control lever may generally be positioned between a neutral and a full forward (and possibly a full reverse) position. The levers are generally sized and configured so that the operator may manipulate the levers over their normal range of motion (e.g., from neutral to full forward) without relocating his or her hands. In the full forward position, the levers may be configured to rest against stationary bars. Such a configuration permits the operator to hold the levers against a fixed stop during normal operation, reducing potential fatigue in the hands, wrists, and arms. The fixed stop may also provide a degree of lever stability, minimizing inadvertent lever movement as a result of vehicle motion.
While effective, this fall forward position may result in a vehicle speed in excess of what is desired for some mowing tasks. To reduce the speed, the operator may back the control levers off from the full forward position. Unfortunately, this technique denies the operator the ability to rest the levers against the fixed stops. Alternatively, the engine throttle may be reduced. While throttle reduction is effective at reducing maximum vehicle speed, it also reduces the power level or rotational speed of any implements, e.g., the mower blades. As a result, cutting efficiently of the mower may be reduced.
To address this issue, some mowers may provide a control lever travel limiter. The limiter may selectively restrict travel of each drive control lever by interposing an intermediate rest or stop that limits lever movement to a position that is less than the normal full forward position of the lever. For example, a typical mower may have a maximum forward velocity of four mph and the control levers may have a corresponding normal maximum travel of four inches. As a result, movement of the levers from the initial (“zero”) position to the full forward (“four inch”) position results in a change in velocity between zero and four mph. The travel limiter may selectively interpose a stop positioned at, for example, three inches of lever travel, such that the vehicle velocity is now effectively limited to a range of zero to three mph. While such a configuration may contribute to ease of operation (the levers may still be held against a stop element at the lower three mph speed), it does not alter lever sensitivity (the ratio of control lever travel to vehicle ground velocity). Moreover, such devices may be time consuming, complicated to operate, and/or difficult (or even unable) to engage while the mower is moving.